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Merge pull request #31604 from neolit123/1.24-add-example-for-kubeconfig-user

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kubeadm: add missing guide for "kubeconfig user"
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Kubernetes Prow Robot
2022-02-08 20:24:17 -08:00
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parent 76429c1a66 75a33b2650
commit 71389e6293
3 changed files with 61 additions and 6 deletions
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content/en/docs/tasks/administer-cluster/kubeadm/kubeadm-certs.md
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@@ -10,7 +10,9 @@ weight: 10
{{< feature-state for_k8s_version="v1.15" state="stable" >}}
Client certificates generated by [kubeadm](/docs/reference/setup-tools/kubeadm/) expire after 1 year. This page explains how to manage certificate renewals with kubeadm.
Client certificates generated by [kubeadm](/docs/reference/setup-tools/kubeadm/) expire after 1 year.
This page explains how to manage certificate renewals with kubeadm. It also covers other tasks related
to kubeadm certificate management.
## {{% heading "prerequisites" %}}
@@ -126,13 +128,13 @@ command. In that case, you should explicitly set `--certificate-renewal=true`.
You can renew your certificates manually at any time with the `kubeadm certs renew` command.
This command performs the renewal using CA (or front-proxy-CA) certificate and key stored in `/etc/kubernetes/pki`.
This command performs the renewal using CA (or front-proxy-CA) certificate and key stored in `/etc/kubernetes/pki`.
After running the command you should restart the control plane Pods. This is required since
dynamic certificate reload is currently not supported for all components and certificates.
[Static Pods](/docs/tasks/configure-pod-container/static-pod/) are managed by the local kubelet
and not by the API Server, thus kubectl cannot be used to delete and restart them.
To restart a static Pod you can temporarily remove its manifest file from `/etc/kubernetes/manifests/`
To restart a static Pod you can temporarily remove its manifest file from `/etc/kubernetes/manifests/`
and wait for 20 seconds (see the `fileCheckFrequency` value in [KubeletConfiguration struct](/docs/reference/config-api/kubelet-config.v1beta1/).
The kubelet will terminate the Pod if it's no longer in the manifest directory.
You can then move the file back and after another `fileCheckFrequency` period, the kubelet will recreate
@@ -289,3 +291,52 @@ Such a controller is not a secure mechanism unless it not only verifies the Comm
in the CSR but also verifies the requested IPs and domain names. This would prevent
a malicious actor that has access to a kubelet client certificate to create
CSRs requesting serving certificates for any IP or domain name.
## Generating kubeconfig files for additional users {#kubeconfig-additional-users}
During cluster creation, kubeadm signs the certificate in the `admin.conf` to have
`Subject: O = system:masters, CN = kubernetes-admin`.
[`system:masters`](/docs/reference/access-authn-authz/rbac/#user-facing-roles)
is a break-glass, super user group that bypasses the authorization layer (e.g. RBAC).
Sharing the `admin.conf` with additional users is **not recommended**!
Instead, you can use the [`kubeadm kubeconfig user`](/docs/reference/setup-tools/kubeadm/kubeadm-kubeconfig)
command to generate kubeconfig files for additional users.
The command accepts a mixture of command line flags and
[kubeadm configuration](/docs/reference/config-api/kubeadm-config.v1beta3/) options.
The generated kubeconfig will be written to stdout and can be piped to a file
using `kubeadm kubeconfig user ... > somefile.conf`.
Example configuration file that can be used with `--config`:
```yaml
# example.yaml
apiVersion: kubeadm.k8s.io/v1beta3
kind: ClusterConfiguration
# Will be used as the target "cluster" in the kubeconfig
clusterName: "kubernetes"
# Will be used as the "server" (IP or DNS name) of this cluster in the kubeconfig
controlPlaneEndpoint: "some-dns-address:6443"
# The cluster CA key and certificate will be loaded from this local directory
certificatesDir: "/etc/kubernetes/pki"
```
Make sure that these settings match the desired target cluster settings.
To see the settings of an existing cluster use:
```shell
kubectl get cm kubeadm-config -n kube-system -o=jsonpath="{.data.ClusterConfiguration}"
```
The following example will generate a kubeconfig file with credentials valid for 24 hours
for a new user `johndoe` that is part of the `appdevs` group:
```shell
kubeadm kubeconfig user --config example.yaml --org appdevs --client-name johndoe --validity-period 24h
```
The following example will generate a kubeconfig file with administrator credentials valid for 1 week:
```shell
kubeadm kubeconfig user --config example.yaml --client-name admin --validity-period 168h
```